1. Field of the Invention
The present invention relates to a pattern sewing machine and more particularly to a pattern sewing machine which is provided with a fabric transfer means for transferring fabric in a lateral direction.
The present invention relates to a pattern sewing machine, and more particularly to a sewing machine which selects a combination of pattern units such as characters and signs and forms the combination of pattern units in a line on a fabric by driving a sewing mechanism and a fabric feed mechanism.
2. Related art
A conventional pattern sewing machine can sew a plurality of two-dimensional patterns such as characters and signs on a fabric. It has been proposed to provide this type of pattern sewing machine with a function to rock the sewing needle in a lateral feed direction which is parallel to the axis of the arm of the sewing machine. Another proposed function is to transfer the fabric in the lateral feed directions as well as back and forth in a primary feed direction which is at a right angle to the lateral feed direction. With these functions a pattern sewing machine can sew selected patterns in different sizes.
Such a sewing machine has a memory of a set of needle location data for sewing each pattern and sews selected patterns in a sewing order based on the needle location data. To change the size of a pattern, the distances among the needle locations are either widened or shortened. The change of the distances is achieved by changing the rocking amount of the sewing needle or the feed of the fabric.
In the conventional pattern sewing machine, characters, signs, or other patterns (referred to as pattern units hereinafter) are usually sewn in a straight line. Furthermore, if some pattern units such as letters, which have a direction, can be rotated by 90.degree. when they are sewn, such unit patterns can be sewn in two different arrangements. The space between pattern units can be altered in the primary feed direction by changing the feed amount per feeding operation, the maximum feed amount being several millimeters per feeding operation. However, pattern units cannot be sewn out of the straight line; that is to say, the line of the pattern units cannot change its course in the lateral feed direction. For instance, the pattern unit B of the combination of the pattern units A, B, and C cannot be moved in the lateral feed directions shown in FIG. 7 because the lateral feed amount can not be accurately controlled. The maximum lateral feed amount per operation is as small as approximately 0.7 mm; so if the lateral feed amount is adjusted, for example, to 0.2 mm, the actual feed amount no longer corresponds to the feed amount supposedly obtained by the feed dog due to friction or stretch of the fabric, thus controlling the lateral feed amount is difficult.
Therefore, the conventional pattern sewing machine, even though it can automatically sew complicated pattern units, must have an operator adjust the position of the fabric in order to sew a pattern unit out of a straight line in the lateral feed direction. However, the manual change of the fabric position may not produce a neat and well-balanced arrangement of pattern units on the fabric.
Furthermore, in the conventional pattern sewing machine, the direction in which the combined pattern units area sewn is limited. Therefore, it has not been possible to sew pattern units in a variety of sewing directions other than in the straight line in the primary feed direction. A sewing machine which can sew a previously unattainable formation of combined pattern units will greatly enhance the aesthetic value of patterns.